It will be a long time, decades at least, before computer control technology is adequate to build contained, on-board systems which can be trusted to do a better job than humans do with the incredibly complex task of driving in traffic. Even if technology were up to the task, it would take a decade or more to replace most of the privately owned motor vehicles. But there is a great need now for a technology which could improve traffic flow on existing roads and freeways. Such a technology would alleviate the need to build freeways in places where there is no room for them, and significantly reduce pollution since a large fraction of vehicle pollution comes from low speed or idling engines.
While current computer/electronic technology is not up to the task of driving vehicles, advances in this field over the last decade or two have been significant. A simple way to think about the changes which are continuing to revolutionize the electronics industry is that striping roads with four-function calculators, instead of paint, would only add ten dollars to fifteen dollars a foot (fifty thousand to seventy-five thousand dollars per mile) to the costs of a lane. Freeway lane expansion (where possible) costs at least a million dollars a mile. If striping lanes with four-function calculators improved traffic flow even ten percent, it would be cost effective.
It is desirable to provide detailed speed and spacing instructions to drivers by means of a computer controlled, sequentially activated, lighted section of a string of lights in a strip glued near the center of each lane of a freeway or road. This system would provide sensitive position feedback information to drivers from computers able to optimize overall traffic flow, and thus permit higher levels of traffic than are possible for unaided drivers. Among the functions of such a strip would be to delay the onset of "emergent" phenomenon (of which massive slowdowns and standing waves are examples) at traffic levels near saturation, that is levels where traffic flow becomes unstable. A best guess from observation of traffic in collapse or near collapse conditions is that a fifty percent or greater improvement over the level E service of 1800 to 2000 vehicles per lane per hour might be possible.
Various U.S. patents in the past have dealt with techniques for providing control of traffic.
U.S. Pat. No. 3,872,423, issued on Mar. 18, 1975, to J. Yeakley, describes a pacer system and a method of spacing moving vehicles along the traffic lane. This provides a "pacing signal" for selectively displaying an indicator which is timed with respect to other means so as to provide a "continuous signal" corresponding to the proper vehicular speed along the lane. By keeping pace with the signal as it appears, a vehicle can be maintained at a programmed speed. The vehicles can also be maintained at a substantially fixed distance from a vehicle in front and a vehicle in back. The signals are programmed for each indicator so as to space successive vehicles apart at a distance corresponding to the programmed speed for the vehicles and the time interval from one displayed pacing signal to the next. A plurality of lights are built along the side of the highway so as to provide the pacing signals. In this invention, there is no feedback interaction with the individual vehicle travelling along the highway.
U.S Pat. No. 3,750,099, issued on Jul. 31, 1973, to R. E. Proctor describes a different type of pacing system. This invention is comprised of a stationary strip of equally spaced bars transverse to the direction of traffic and suitable means for intermittently illuminating these bars simultaneously at a selected frequency. The frequency selected is designed to produce a stroboscopic effect on the observer moving parallel to the strip of bars. Only at a predetermined velocity will the bars appear to be motionless. At a velocity near, but greater than the predetermined velocity, these bars will appear to the observer in such a manner that he is overtaking the bars. At a velocity near, but less than the predetermined velocity, it appears to the observer that the bars are moving away from him. Once again, this provides a stroboscopic pacing system but without the feedback from the vehicle.
Another traffic pacing system is also shown in U.S. Pat. No. 3,188,927 issued on Jun. 15, 1965, to A. M. Woods. This device also uses a system of dots that are ingrained into the highway and illuminated so as to allow the moving vehicle to remain a proper distance behind another vehicle. These lights in the roadway are arranged to illuminate at predetermined intervals. This is a rather simple invention used for indicating proper spacing of vehicles.
U.S. Pat. No. 3,529,284, issued on Sep. 15, 1970, to C. A. Villemain shows a traffic control system. This is a sequential series of traffic control lights that are mounted on the roadway so as to be visible from a single lane and by a single vehicle only. These lights are sequentially energized with green, preferably in intermittent flashes, to form a progressive wave of blinking lights for the control of individual vehicles travelling in a group at a speed determined by the progressive blinks. The cycling of the control lights can vary, in accordance with the number of vehicles and their maximum speed, as controlled by computers which count the number of vehicles intended to enter a given controlled roadway or lane. Once again, there is no feedback between the progression of the signals and the location of the vehicles on the roadway.
U.S. Pat. No. 3,593,262 describes a traffic control system for a merge junction between first and second vehicular paths. This provides a warning to the vehicles ahead. It is very Similar to the kind of block control used on railroads. It could be quite useful for fog conditions. However, it does not function for positive position control.
The present invention proposes to glue on roadways an amount of electronic circuitry about equal to a continuous string of four function calculators, and to dedicate substantial computer resources to controlling those circuits.
The present invention is predicated on the following: First, people generally do a good job of driving vehicles and could be trusted to follow directions from computer system directing traffic. This is only an extension of our long experience with traffic lights. Second, the cost of dedicating what is now a large personal computer per lane per mile is not excessive compared to the cost of pouring concrete. Third, visual and infrared solid state devices are sufficiently long lived, inexpensive, and rugged enough that they could be encapsulated in clear plastic and glued to roads with the expectation that they would last for some years--even with heavy trucks running over them.
With the above in mind, the object of the present invention is to provide substantial improvements (estimated at 50 to 100%) in traffic flow at very high traffic levels, particularly at those levels of traffic which result in "stop and go" driving conditions.
It is an object of the present invention to provide a traffic control system that, through visual signals to the drivers, or directly, through interaction with vehicle cruise controls, has control over the longitudinal location of every vehicle in the traffic stream.
It is another object of the present invention to provide a traffic control system that has bidirectional interaction with the drivers of individual vehicles on the highway.
It is still another object of the present invention to provide a traffic control system that can monitor highway conditions locally as well as far ahead and adjust traffic speed and spacing to compensate by providing signals to the drivers.
It is still a further object of the present invention that the signals it provides be intuitive to drivers.
It is still a further object of the present invention to provide a traffic control system that is relatively inexpensive to install.
It is still a further object of the present invention to be useful without requiring any vehicle modifications to be made.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.